Take a tail light with a similar form to the dinote ( for example ) incorporate a flashing circuit, and an accelerometer. Under normal usage, it has a, fairly fast flash. As you start to slow, so does the flash, When you grab a handful of brake, it comes on solid red, maybe an increase in brightness too?

I used 4 super bright (amber), large (22 LEDS per unit) LED strobes to create turn signals and super bright (red) LED strip to make a brake light this summer. (So many younger drivers interpreted the hand signal for a right turn as a wave, I decided turn signals were a must and while I was at it I thought why not install a brake light.) I used a micro lever switch, set to normally open, zip-tied to the brake cable for controlling the light--when I depress the rear brake, the brake light is activated. Both the strobes and the strip I use for the brake signal require so little power that I use a 9V battery (1 9V for the 4 turn signals and 1 9V for the brake light). Best of all, my cost was extremely low--the micro lever switch was the most expensive component at $9.00--the rest--LED strobes, LED strip and a center-off-toggle switch (for the turn signals) cost a total of $20.

Sorry for the quality of this first picture (I took it in the middle of installing everything and didn't take the time to see that I hadn't focused the camera), but here's the brake light--I have a good, battery-powered tail light/blinker so the brake light is simply a brake light and it's right below the tail light.

You see the rear turn signals, brake light and my tail light in this shot. If I upgrade the brake light in future, it will be to get a larger LED strip.

i honestly don't think bikes should have this stuff because cars will rely on it. anytime a car sees a bike it should immediately think "need to pay attention!"... and you should be lit up enough already that a car will already see you and already see that you're stopping, turning, signaling(sometimes i hand signal as well as point, i'm turning into THIS driveway) or whatever.

however if it were possible, i'd rather have a controllable array of super bright P7 lights or whatever, so you have two yellow lights and a red brake that may be very dim for running.